The long term objective of this research is to develop a comprehensive multivariate theory of acute adverse reactions to psychcactive drugs that will have predictive as well as explanatory capacities. The specific aims of this study are: (1) to further develop measures of acute adverse reactions, (2) to conduct a exploratory interview study of Ss who have experienced acute adverse reactions in order to develop hypotheses about situational and setting determinants of these reactions, (3) to develop comprehensive questionnaire which will include operational measures of those elements of situational, set, and personality variables related to the development of acute adverse reactions, and exploratory hypotheses concerning long term effects of these reactions, and (4) to develop a series of theoretical mathematically stated models of increasing complexity that will specify the relative importance of factors related to the development of acute reactions. The most comprehensive model that can be derived from this cross sectional data would be used as the initial model in the first phase of a longitudinal study, planned to begin at the completion of this project period. The data will consist of exploratory interview responses from approximately twenty users who have experienced acute adverse reactions, and from questionnaire data from approximately seven hundred Ss who are current users of psychoactive drugs.